POSCO is seeking to form a consortium to buy the stake with South Korea's National Pension Service and other investors, the source said, but declined to elaborate on the size of the planned stake.
The Korea Economic Daily reported on Tuesday that POSCO has been picked as the preferred bidder for a 15 percent stake in ArcelorMittal Mines Canada, a deal expected to be worth more than $1 billion.
A POSCO spokeswoman said the company is considering a bid for a stake in the mine, but declined further comment, saying the matter is confidential.